Air filter



March 8, 1949. L. SPRARAGEN 2,463,722

- AIR FILTER 5 Sheets-Sheet 1 Filed June 15, 1944 INVENTOR LauzwJ/Jrmuen, BY r ATTORNEYS March 8, 1949. L. SPRARAGEN r 2,463,722

AIR FILTER Filed June 15, 1944 s Sheets-Sheet 2 HEJVENTOR lows 529761211871,, BY

ATTORNEYS March 8, 1949. SPRARAGEN 2,463,722

AIR FILTER Filed June 15, 1944 v .3 Sheets-Sheet 3 Fly. 72 g "In-:-YIIIIIIIII/IIIIII/IIIIIIIIIIIIIIIIQ VIIIIW/IIIIfl/IIIII IIIIIIII/IngvENToR 04m" ,Jwamgeh,

ATTORNEYS Patented Mar. 8, 1949 UNITED STATES PATENT OFFICE AIR FILTERLouis Spraragen, Bridgeport, Conn.

Application June 15, 1944, Serial No. 540,441

1 Claim. 1

This invention relates to air filters, and more particularly to afiltering unit attachable to airsucking equipment such as pumps,internal combustion engines and the like to purify air being used bysame.

Filters commonly used for this general purpose have screening elementswhich in some cases are made of woven or felt cloth, and in other casesare in the form of sponge-like pads made of metallic ribbon. Inpurifying air, the latter type are generally coated with a non-drying orviscous dust-collecting substance such as oil, whereas the clothelements are usually operated dry, and depend on the closeness of theweave and the fibrous character of the material for cleaning the air.

In the case of filters employing metallic pads, the elements are formedby severing a predetermined amount of material from a large supply, andshaping the material usually into the form of an annulus, for insertioninto a supporting housing. When this is done, the interstices of thematerial, which originally are not too uniform in size and shape due tothe lack of resilience of the metallic ribbon and due to handling, arefurther deformed so that a considerable diverging exists when theelement is finally resting in the filter. Moreover, at the point wherethe ends of the element meet, in an annulus, large irregular spaces arecreated, a condition which cannot be readily corrected.

As a result, incompletely filtered air is permitted to enter theequipment through the large openings and interstices of the irregularpad structure, and may under severe and adverse atmospheric conditionscause considerable damage.

Textile cloth or fabric filter elements generally obviate thiscondition, but are more costly to make, requiring especially constructedsupporting structures and more expensive assembly operations. Also, theelements may not be readily cleaned, so that when they become dirtyreplacement with new elements is necessary. Whereas cleaning of themetallic sponge element of air filters may be accomplished in a simplemanner by merely dipping them into a solvent and recoating with freshoil. This procedure would cause sagging and deterioration of thematerial if applied to a textile fabric air-filter element. Also, withtextile fabric there is the likelihood of tearing or unraveling, whichwould defeat the purpose of the filter.

It is an object of the present invention to obviate the abovedisadvantages in filters. This is accomplished by the provision of afiltering unit having comparatively rigid self-supporting screeningelements which are non-deteriorating and provide numerous intersticessubstantially uniform in size and shape and also provide fibroustendrils extending about and into the interstices to intercept andfacilitate the collecting of foreign matter from the incoming air.

Due to the absence of inadvertent large openings either at or betweenjunctures of the screening material, the cleaning of the air isaccomplished uniformly and by the use of fibrous tendrils the dirtcollecting surfaces and areas are greatly increased, and the filteringaction generally improved.

The filter or screening elements may be used in a dry condition tofilter air, or may be coated with a non-drying viscous substance such asoil, depending on requirements, and in either case cleaning of theelements may be carried out without detriment thereto by employing asimple rinsing procedure. The interstices of the elements may beaccurately controlled as to size and uniformity, may be made small orlarge to suit particular conditions, and the elements themselves may beconveniently formed and interfitted if desired to provide consecutivescreenings of the air.

In one form of the invention, the filter elements comprise formed piecesof wire mesh, the wires of which at their points of contact are boundtogether by cement, the mesh havin a uniform coating of flock alsosecured by cement and arranged so that the fibers thereof extend fromthe wires in all directions. According to this arrangement the use ofpieces of pliable textile fabric in a filter, with their accompanyingdisadvantages, is not necessary.

In an illustrated embodiment of this invention, the construction of theunit provides two such flocked elements, each cylindrical, one of largerdiameter than the other, which are concentrically mounted in a housing,and a third element is zigzag folded so that when the ends are connectedit forms a multi-pointed star which may be disposed between the twocylindrical elements.

In another illustrated form of the invention a. plurality of cylindricalconcentrically disposed elements is carried in a holder.

In each of these constructions the air may pass through the elementsconsecutively, the outer one first.

According to the present invention rigid screening elements may be wovenor molded plastic screening, formed of Vinylite or other plasticmaterial, or may be made of expanded metal or paper, formed papier-mach,and the like, with the flock coating secured to the screen through theuse of adhesives suitable to each particular material.

The end of the screen elements may be bound with a soft textile fabricso as to seal the same and housing plates between which the screenelements are located. Or a felt strip may be interwoven in the mesh,when the elements arebeing made so that when the mesh is cut to dividethe felt strip, the cut edges of the mesh have felt edging whichfunctions as a gasket at the points where the filter housing engages theedge of the screens. Also, the surfaces of the housing which engage andsupport the elements may-be heavily coated with a yieldable materialinto which the edges of the mesh may be embedded, to provide anair-tight connection.

A novel supporting or housing structure provides for quick andconvenient removal of the elements for cleaning purposes, yet preventsleakage past co-engaging surfaces. By this construction replacement of'the elements may be quickly accomplished also.

Other features and advantages will hereinafter appear.

In-the accompanying drawings- Figure 1 is a top view of a filtering unitmade according to the invention, with the top plate of the housingremoved.

.Fig, 2 is an axial section .taken on the line -2--2 .of Fig. lgparts ofthe screens being shown diagrammatically.

Fig. 3 is aperspective viewof the central supportingwtube .of the unit.

Fig. .4 is a perspective view of the top closure .forthe tube.

Fig. .5 is a-perspective view of .an end plate carrier for thestar-.shaped'filter element.

Fig-6- is .a fragmentary elevational detail of the filter meshconstruction, showing the largemesh employedin the outer cylindrical,elementof the filtering tunit.

Pier-7 is similar to Fig; 6,.butshows the smaller mesh employedintheinner-cylindrical element of the unit.

.Fig. 8is-aperspective view of the .zigzag folded mesh .for thestar-shaped .intermediate element. before beingexpanded andformed tofinalshape.

Fig.9 is an enlarged fragmentary sectional view .of a folded edge of anelement made according tozthe invention.

.Fig. 10 is atop view'of amodified form .of filtering unit, with thetop-plate of the housing removed.

Fig. 11 is a top view of another modified form of filteringunit, tophousing plate removed.

Fig. 12 is a side elevation, partly in section, of

vanother modified form of .filtering unit, for .mounting with its axishorizontal.

Fig. 13 is atransverse section taken on theline .|3l3 of Fig. 12.

Fig. 1.4.is. a transverse section taken on the line M-l 4 ofFig. .12.

The filtering .unit shown in Figs. 1 through 9,

which may be advantageously used to filter intake air for thecarburetors of internal combustion engines, for pumps and the like, hasa housing comprising. a central tubular stem 20 which carries circularbottom and top plates 2| and 22, respectively. The bottom plate 2] hasan upturned central flan e 2la which snugly fits the outside diameter ofthe stem 20 and is spot Welded I thereto as indicated in Fig. 2.

The-top end of the stem "2ll-is provided with a formed sheet metalclosure 23 which fits snugly inside the stem and is also spot weldedthereto (Fig. 2). The closure 23 is at its center extruded and threadedto carry a stud 24 extending through the center of the top plate 22, awinged nut 25 being provided for demountably securing the top plate tothe stern.

According to the invention the bottom and top plates '2! and 22 areshaped to carry the selfsupporting filtering elements of the unit, andfor this purpose as shown in Fig. 2 the peripheral edges of the plateshave flanges 2H; and 22a respectively, extending toward each other.Carried between the top and bottom plates in engagement 0 with theflanges 2 lb and 22a is a novel comparatively rigidself-supportingfiltering element 26. This element is of wire mesh having a coating offlock disposed on it in such a manner that the fibers thereof extend inall directions from the wires. forming dirt-collecting tendrils whicheffectively filter and clean air which may pass through the element. Theflock may be deposited on the mesh by being blown against it, and madeto adhere to the wires by a suitable adhesive or cement, whichmay alsobind the wires themselves where they cross. As shown in Fig. 1 theflocked mesh is formed into a cylinder which fits closely inside andagainst the flanges Zlb and 22a of the top and bottom plates. thejoining edges of the cylinder being secured by a clamp strip 26a havinglanced fingers 28b which pass through the interstices ,of the mesh andare folded over on the latter at the inside. The filtering element 26 asthus constructed is substantially rigid so that it may be firmly heldbetween the top and bottom plates of the filtering unit by drawing theseplates together by means of the winged nut 25. Due to the engagement ofthe flanges 21b and 22a with the filtering element 26 at the open endsthereof,

.: a seal is effected so that the likelihood of air by passing theelement at its edges Without being filtered is minimized.

A second self-supporting cylindrical filtering element 21 locatedclosely adjacent and concentric with the stem 20 is also provided. Theelement 2! is coated with flock substantially in the same manner as thecylindrical element Ziiand has a diameter to fit closely around thecentral flange Zia of the bottom plate. For the purpose of centralizingit at the top plate, the latter is embossed to provide a downwardlydished center portion 22b closely fitting inside the upper end .of theelement 21. The meeting ends of the element 21 are joined in a, mannersimilar to that used for the element 25, by a clamp strip 270. havinglanced fingers 21b, as shown in Fig. l.

The invention also provides another noveland self-supporting filteringelement 28 in the form of a multi-pointed star which is disposed betweenthe elements 26 and 2.1 to provide somewhat of a tortuous path for theair passing through the filter unit. The element 28 is of flocked mesh,being shaped by initially zigzag folding it into a pack as shown in Fig.8, in which form it may be conveniently handled for shipment,replacement, etc. The detail shown in Fig. 9 illustrates the bending ofthe mesh, as at one of the points of the star. For supporting thestar-shaped element 28, a pair of identical spacer rings 29 and 3B] areprovided, one such ring being illustrated in Fig. 5. Referring to Fig.2, the bottom and top plates 2i and 22 of the filter have embossedcircular beads Mo and 220 respectively, adapted to engage and centralizethe spacing rings '29 and 3B, the latter having cylindrical fianges'ZSaand 30a respectively, engaging the inner bends of the star, and alsohaving pluralities of fingers 29b and 38b which are lanced from therings for clamping selected bends of the star to the flanges. As shownin Fig. 1, the meeting ends of the element 28 are overlapped in themanner indicated.

Preferably the star-shaped element 28 is provided with'cloth bindingstrips 28a and 281) which are folded over the bottom and top edgesrespectively. These strips, which may be cemented in place to securelyhold them, may function as gaskets in engaging the inner surfaces of thetop and bottom plates to prevent the passage of air at these points.

The filtering unit is adapted to be mounted on an air intake pipe bymeans of the stem 20, the air supply to flow through the bore of thestem. As shown in Figs. 2 and 3, for this latter purpose the walls ofthe stem 2|] are cut away to provide a pair of oppositely locatedenlongate slots a. and 261) which open into the interior of the element21.

By this construction suction applied to the stem 20 will cause air to besucked through the elements 26, 28 and 21 consecutively in the ordergiven. As is often customary in air filters, the elements may be coatedwith a viscous non-drying substance such as lubricating oil, so that thedust-collecting action of the flock is enhanced. According to theinvention by the provision of the upturned flanges 21a and 2lb on thelower plate 2!, the latter may carry a quantity of oil when thefiltering unit is mounted with its axis vertical, this oil traveling bycapillary attraction up the elements 26, 21 and 28 and maintaining adirt-trapping coating or film on the flock. Preferably the size of themesh of the element 26, pictured in Fig. 6, is larger than that of theelement 28, and the latter in turn larger than that of the element 21,pictured in Fig. 7, as an example, the element 26 may be ten mesh, theelement 28 fourteen mesh, and the element 21 sixteen mesh. This isadvantageous since the speed of the air flow through the element 26 isslower than through the element 28, and the speed through the element 21faster than through the element 28.

The filter elements 26, 21 and 28 being comparatively rigid, will beadequately supported by the respective associated parts of the housingof the unit, and will not loosen if the unit is subjected to vibrationsnot greatly in excess of those normally encountered. In connection withthis, the reinforcement provided by the cementitious binder at thepoints where the wires of the mesh cross each other contributes to themechanical stability and strength.

If, as a result of damage, or clogging of the mesh due to long continueduse, it is desired to remove the elements, this may be quickly andconveniently accomplished by loosening the winged nut and removing thetop plate 22. The elements may then be easily lifted out and eithercleaned by dipping in cleaning solution, or replaced with new.

If the filter is to be used where it is desirable to have an oil orother viscous coating on the elements, the nature of the cement oradhesive used to secure the flock to the wire should be such that itwill not be affected by this coating, nor the cleaning solution employedto remove the coating in cleaning the element.

A modified form of the invention is shown in Fig. 10. According to thisform'a single selfsupporting filtering element 3| of flocked mesh shapedlike a multi-pointed star is mounted between the plates 21 and 22 sothat the points of the star engage and are positioned by the flanges 2Iband 22a. Preferably the top and bottom edges of the mesh of the element3| are provided with folded cloth binding strips, as in the case of theelement 28, to act as gaskets and prevent by-pass of air withoutfiltering.

By forming the element 3| in the shape of a multi-pointed star, a largesurface area is presented for the passage of air, so that the speed offlow is reduced, thereby resulting in a more effective removal of dust,dirt, etc.

In another modified form of the invention, shown in Fig. 11, a pluralityof concentric cylindrical flock-coated mesh filtering elements 32, 33,34 and 35 are provided, nested one within another. The outermost element32 fits closely within the peripheral flanges of the top and bottomplates, the latter only, designated by the character 36, being shown,with flange 36a.

For spacing the elements in concentric positions, the bottom and topplates are embossed to provide knobs 31 which are located as shown,

' engaging the edge portions of the elements and preventing movement ofsame.

The meeting edges of the cylindrically formed mesh elements are securedtogether by folding to form interlocked seams 38 which prevent bypass ofair along these edges.

Due to the elements having surface areas which are graduated, the speedof air flow through the respective elements is also graduated, andpreferably the size of mesh is chosen accordingly, the outermost elementhaving the largest mesh, and the innermost the smallest.

Also, preferably the end portions of the cylindrical elements areprovided with folded cloth binding strips which engage the end platesand function as gaskets.

An air filtering unit adapted for mounting with its axis horizontal isshown in Figs. 12, 13 and 14.

As shown, a housing isprovided comprising a pair of circularsubstantially parallel end plates 39 and 40, the plates having inwardlyextending peripheral flanges 33a and 48a, and central inwardly dishedportions 3% and 48b respectively.

Each plate is centrally apertured to receive a bolt 4! which, by meansof a nut 42, holds the end plates from separating.

A self-supporting cylindrical flocked mesh filtering element 43 ismounted between the plates 38 and 40, the ends of the element fittingclosely about the dished portions 3% and b for positioning thereby.Engaging the exterior surfaces of the flanges 39a and 48a is aself-supporting semi-cylindrical flocked mesh element 44, the twostraight edges 44a of which (Figs. 13 and 14) are clamped between foldedstraight edges 45 of a concavo-convex mounting plate 46 which latteralso engages the outside surfaces of the flanges and complements theelement so that together they form a complete cylinder.

The filtering element 44 and plate 46 are securely clamped to theend-plates 38 and 40 by bands 41 and 48 which may be tightened by bolts49, as shown in Fig. 12.

In addition to the cylindrical filtering elements 43 and 44, aself-supporting star-shaped fllocked mesh element 50 is mounted betweenthe end plates, the straight edges 50a of the element being hooked underthe folded inturned edges 45 of the mounting plate.

Referring to Fig. 12, the inner surface of the end plate .39 is covered'or coated with a yielding substance 3390 such as rubber, the syntheticThiokol being for instance suitable, so that when the-filtering elementsare properly positioned and the end plates 39 and 40 drawn together bythe bolt 4|, prior to finally tightening the bands 41 and 48, the edgeof the star element 50 will be embedded in the rubber and the latterwill function as a seal toprevent by-pass of air.

. An-alternative structure for accomplishing the same result is alsoshown in Fig. 12, in connection With the end plate 40. A strip of feltis interwoven in the edge of the element 50, so that when the plate 40is held against the edge the felt will be engaged and seal all openings.

In making up the element 50 for use with felt sealing strips, the meshmight be fabricated in large widths with a wide strip of felt interwovenat regular intervals, and the elements then formed by cutting the meshalong the center lines of the felt strips, so that each edge formed bythe cut would have an interwoven felt strip.

In assembling, when the elements 4-3, M and 50 have been mounted betweenthe end plates 39 and 40, the tie bolt 4| is tightened to draw togetherthe plates, which thereby clamp the elements 43 and 50 between them. Thebands 47 and 48 are then tightened, securely clamping the mounting plate46 and element M to the end plates.

For the purpose of supporting the filter unit on an air intake pipe of acarburetor or the like, a tubular stem 52 is provided passing radiallythrough the center of the mounting plate 49, which is formed to receiveit, and into the cylindrical element 43, the stem being rigidly fastenedto the plate. As shown in Fig. 13, the mesh of the element 43 is formedto fit closely to the outside of the stem 52, and may be welded orotherwise fastened to the latter.

The connections between the end plates 39, 40 and the mounting plate 46,and between the latter and the stem 53 are preferably leak-proof so thatoil or other viscous liquid may be placed inside the mounting plate tomount by capillary attraction on the filtering element 50.

The self-supporting flock-coated filtering grids of the presentinvention may be formed of stamped sheet metal, perforated paper, or ofwire mesh both metallic or non-metallic. With re gard to the latter themesh may be made of wires of Vinylite or other suitable plastic. Or thegrids may be made of expanded metal, expanded paper, papier-mach and thelike, depending on the use, in each case the adhesive for securing theflock to the grid being chosen with particular reference to the gridmaterial.

Where comparatively soft materials are used in constructing thefiltering grid, the portions of the latter which engage the end platesmay de- Number form slightly when the plates are drawn together, andconform closely to the plate surfaces, making gaskets unnecessary.

Variations and modifications may be made within the scope of thisinvention and portions of the improvements may be used without others.

I claim:

An air filtering unit comprising a pair of spaced substantially parallelcircular plates each having a pair of circular flanges one at itsperiphery and the other adjacent its center, extending toward the otherplate; a tubular support for the plates, of smaller diameter than theflanges thereof, extending from the center of ne plate through thecenter of the other and rigi ly fastened to the latter, the protrudingend of he support being adapted to connect to an air ntake line, andsaid support having an aperture opening into the space between theplates for passage of air; a pair of cylindrical grids having thesurfaces thereof covered with flock, mounted between the plates,respectively engaging the peripheral and center flanges thereof to bepositioned thereby; a pair of rings having flanges mounted against theinner surfaces of the circular plates, said plate having means forpositioning the rings centrally of the plates; a zigzag grid coveredwith flock, mounted between the plates and engaging the flanges to bepositioned thereby, said grid extending in a star-shaped path betweenthe cylindrical grids so that air entering the aperture of the supportwill first pass through the grids consecutively and be filtered thereby;and means demountably fastening said one plate to the support so thatthe grids may be demounted when the plate is removed.

LOUIS SPRARAGEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Young Oct. 13, 1903 Dunlap Apr. 19, 1910Blanchette Feb. 2, 1915 Foster Mar. 13, 1917 Porter Mar. 27, 1917Goodloe Jan. 29, 1929 Slauson Sept. 24, 1929 Orem Aug. 11, 1936 CampbellFeb. 6, 1940 FOREIGN PATENTS Country Date 1 France Oct. 30, 1936; FranceOct. 14, 1938 Great Britain Mar. 6, 1930 Great Britain May 11. 1933Number

